Method and apparatus for television



June 23, 9 I P. c. GOLDMARK 2,287,033

METHOD AND APPARATUS FOR TELEVISION Filed May 28, 1938 8 Shets-Sheet 1 K R 4 0M 0 2 m6 6 w i, P

ATTORNEYS June 1942- P. c. GOLDMARK METHOD AND APPARATUS FOR TELEVISION 8 Sheets-Sheet 2 Ju ne 23, 1942.

P. c. GOLDMARK METHOD AND APPARATUS FOR TELEVISION Filed May 28, 1958 8 Sheets-Sheet 3 W W B M ATTORN EYS June 23, 1942. P. c. GOLDMARK METHOD AND APPARATUS FOR TELEVISION 8 Sheets -Sheet 4 Filed May 28, 1958 M M M M w MM |1 T0 v 1 mm I: l hhhUuhhwhlH I h l x p VW @x k m R u :5. k .7 A I r m w III, l I I I I aw w.w H: W M Q w m MFM WATTO RNEY5 June 23, 1942.

. P. C. GOLDMARK METHOD mm APPARATUS FOR TELEVISION Filed May 28, 1938 s Sheets-Shet 5' INVENTOR C. GOZDMAfi/f ATTORNEYS June 23, 1942. P. c. GOLDMARK 2,287,033

METHOD AND APPARATUS FOR TELEVISION Filed May 28, 1938 w a Sheets-Sheet s INVENTOR P5227? c. GOLflMA/P/f ATTORNEYS June 23,1942. GOLDMARK 2,287,033

METHOD AND'APPARATUS FOR TELEVISION Filed May 2a, 1938 a Sheets-Sheet 7 ATTORNEYS 8 Sheets-Sheet 8 M m m N QD NW n l6 a I M. m

'June 2- P. c. GOLDMARK METHOD AND APPARATUS FOR TELEVISION- F'iled May 28, 1938 QM k Jw Q ill/W- used in television transmitters. especially relates to a method and apparatus for Patented June 23,1942

'UNIZTED STATES PATENT OFFICEy,

METHOD AND APPARATUS FOR TELEVISION Peter C. Goldmark, NewYork, N. Y., assignor to Columbia Broadcasting System, Inc., New York, N. Y., a corporation of New York Application May 28, 1938, Serial No. 210,607

19 Claims. (01. 1787.2)

This invention relates to television scanning systems, particularly to film-scanning systems tinuously moving film in which a single filmframe is scanned a plurality of times.

In the present state of the art, the televising of program material recorded on film is of considerable practical importance. This is true not The invention only because of the possible extensive use of the for each picture transmitted. In motion picture practice, however, sound films are recorded and projected at the rate of 24 pictures per second. Thus, if standard sound motion pictures are employed in television, these two different standards must be coordinated, and since the periodicity of the scanning is not an integral multiple of the rate of movement of the film in frames per second, a special scanning scheme is required. Such coordination is highly desirable, since it renders the great libraries of ordinary sound-motionpicture film available for television'purposes- Of course, the standards may be changed from tim to time, but it appears likely that the rate .of component scansions in television will be different from the rate at which sound motion pictures are recorded and projected.

Apparatus employed in televising motion .pic-

ture material recorded on film may be classified into two general types. In one type the film is moved intermittently in a manner analogous to that employed in ordinary motion picture practice. In the other type the film is moved with continuous uniform motion.

Apparatus of the first type has been suggested, utilizing a tube of the iconoscope type. The filmframe, while stationary, is projected onto the mosaic of the iconoscope, the projection light cut off, and the image on the mosaic scanned. Successive frames are scanned alternately 2 and 3 times at the rate of 60 scansions per second. In the frames which are scanned three times, the third scansion is a duplicate of one of the other two. Thus, 24 frames of the film are transmitted in a second, but 60 scansions are employed for doing so, thereby coordinating the motion picture and television standards. To accomplish this, however, it is necessary to move the film intermittently at the alternate rates of 30 frames per second and ZOframes per second,

instead of moving the film intermittently at a uniform rate as in ordinary motion picture practice. Thus, the intermittent-feed mechanism is additionally complicated over that employed in Apparatus of the second type above mentioned,

in which the film is fed with continuous uniform motion, and in which film-frames are transmitted at the rate of 24 pictures per second but with 60 scansions per second, have been disclosed in my prior copending United States applications, Serial Numbers 72,009 and 115,113. 'In the embodiments there shown, the scanning pattern of the scanning cathode-ray tube is displaced for successive scansions in such a manner that the film-frames are scanned alternately two and three times, thus scanning 24 film-frames with 60 scansions. This procedure gives the desired coordination between the motion picture, and television standards.

The present invention is particularly concerned with apparatus of the second type in which the film is moved continuously. It differs from the systems in my prior applications above mentioned, however, in that the relatively large displacement of the scanning pattern of thescanning device is avoided, and .the necessary displacement produced by optical means, the scanning pattern itself remaining stationary. This procedure has certain advantages as regards simplicity of equipment, reliability of operation, and quality of the reproduced pictures. A further difference is that in the apparatus described herein the images on the film are optically projected to the scanning device, instead of optically projecting a scanning spot of light to the film. Thus an adequate amount of light, which is important in television scanning, may be secured, and this light may be used eflicintly, Furthermore, this procedure renders possible the use of electronic sector type. Also, excellent contrast and detail may be obtained.

The invention is particularly advantageous in connection with present day electronic scanning tubes. image-dissector type, for which the invention is particularly adapted, it is found that the deflecting fields in different parts of the tubes are not absolutely uniform. With pictures of the high definition now employed (441 lines per picture is the present standard), if two interlaced scansions of a single film-frame are produced in different parts of the scanning tube, such non-uniformity of the deflecting field in the two respective parts of the tube will prevent the precise interlacing of the two scansions, and hence will adversely affect the quality of the television image. Also, if two scansions of a single film-frame were each complete, rather than interlaced, the two images would not be identical, and hence would impair the received image. Still further, it is possible that inthe development of the art it may become desirabl 'toascan fewer pictures per second than are recorded on'the film, so that individual filmframes would be scanned only once, but at different points in their path of travel. In such case, if successive film-frames were scanned in different parts of the scanning tube, non-uniformity of the deflecting field in the two respective parts would adversely affect the quality of the transmission since usually successive film-frames differ only slightly from each other.

By not displacing the scanning pattern, the present invention avoids the above difficulties.

Furthermore, the required working area of the scanning tube is smaller than that'required when the scanning pattern is displaced, for a given magnification between film-frames and scanning device. Even when it is desired to employ a mechanical rather than an electronic scanning device, -for example, an apertured disc, using the scanning scheme described hereinbefore, the invention permits of the use of a simpler scanning device than would otherwise be the case.

In accordance with the invention, portions of a film lying at different separated areas in the path of travel of the film are successively projected and rendered in scanning relation with a substantially stationary scanning pattern produced by a suitable scanning device. More specifically, portions of a film lying at different separated fixed areas in the path of travel of the film are projected to substantially the same area of a selected image surface, usually a plane, and a scanning device is positioned with respect to the plane so as to scan the projected images of those portions of the film lying at the separated areas as they are projected to the same area of the selected plane.

Several forms of apparatus have been devised to carry out the above procedure, and will be described hereinafter. Although each of these forms is adapted'to carry out the method of the invention, in general different forms possess 60 somewhat different advantages from a practical standpoint, and therefore the particular form selected will be chosen in view of the particular conditions surrounding the application.

In general, a projection system is employed including optical means successively operative to project different relatively spaced areas in the path of travel of the film to the scanning device. Forexample, a plurality of successively operative In such tubes, for example, in tubes of the scanning tubes such as those of the "image-dls- 1 light-diverting elements, such as lenses or mirrors, may be employed.

One embodiment described hereinafter employs a plurality of projection lenses spaced apart in the direction of travel of the film. This embodiment is comparatively simple in design. The lenses will be ordinarily rather small, but should preferably be rather highly corrected. Furthermore, the several lenses should have the same focal length, unless some compensating means is employed. If desired, portions of highly cor- ,rected systems may be employed.

Embodiments employing a single projection lens, which may be of standard design, have also been devised. In general, these embodiments employ one or more light-diverting elements, for example, mirrors, for producing the relative displacement at the'film. In one such design, a single mirror is employed, with a mechanism for .intermittently changing the orientation of the mirror through a plurality of different orientations, thereby making efficient use of the light passing through the projection lens.

With relatively high frame frequencies, it may be difficult and expensive to construct apparatus to change the orientation of the mirror with the desired rapidity and precision. For such a case, apparatus has been devised employing a plurality of fixed mirros whose orientations are such as to produce the desired separation of the areas of the,

film. In such a system the mirrors are relatively inexpensive and permit of a comparatively wide latitude of adjustment.

Inthe systems hereinafter more fully described, in which images on a continuously moving film are optically projected to the scanning device, it is-contemplated that a single film-frame, ordinarily, will be successively projected a plurality of times and scanned each time. In view of present standards, the apparatus is designed to scan each film-frame a plurality of times, successive frame areas being scanned two and three times. If the standards are changed, or if for any other reason it is desired not to scaneach film-frame a plurality of times, the apparatus of the invention may be changed accordingly.

Generally, the film-frame will be in a different position in its path of travel at the beginning of each scansion period. Also, since the film is moving during each projection, the image at the scanning device will be moving. In accordance with the method of the invention, at corresponding instants in the respective scansion periods the projected ima'gesof a given film-frame occupy substantially the same area of the scanning device. Thus, the projected images of a given element of the film-frame occupy substantially the same elemental area of the scanning device each time that-particular element is scanned.

For convenience, it may be considered that at corresponding instants in the respective scansion periods the projected images of the same film-frame coincide at the scanning device. It will be understood that the images are not there at the same instant, but are there during their respective scansion periods.

Ordinarily, successive frames of a film will have the same dimensions and will bear images only slightly differing from each other. fore, at corresponding instants in the respective scansion periods, not only the several images of the same film-frame but also the images of successive film-frames are projected to the same area 'of the scanning device. Thus the scannin pattern may remain unchanged for successive Thereseparated points a'. b', c', d and e' in the path of travel of film ll pass through the respective and successive film- Fig. 1 is'a diagrammatic view, partly in section, of transmitting film-scanningapparatus employing a plurality of projecting lenses;

Fig. 1a is a front view of the projection lamp of Fig. 1;

Fig. 1b is a front view of the projection lenses of Fig, 1;

Fig. 2 is a front view of the shutter employed in Fi l; a I

Fig. 3 is a diagram illustrating the operation of the apparatus of Fig. Land also the general projection lenses and are superposed at point 23 the cathode of the image-dissector tube, assumingv for-the moment that all the projection lenses are in operatioirat the same time. If the principles of operation of the apparatus shown,

in the remaining figures of the drawings;

Fig. 4 is a diagrammatic view, partly in section, of film-scanning apparatus employing an film II were considered to be stationary, the spaced points a, b, c, d, e could be considered as being spaced points of the film itself. But since the film is continuously moving, the points ,of the film which lie at points a a will be continuously changing, and therefore the points on the film which are superposed-at point 22 will be continuously changing. However, the points of the film which are superposed for one position of the film remain superposedas the film moves, the point on cathode 24 at which they are superposed changing with the film movement.

Actually, in the operation of the apparatus, only one projection lens is operative at a time, and the lenses are made successively operative in the proper sequence by means of a continuous- 1y rotating shutter 25 driven by motor l4. Since motor l4 \drives both the fil1nfeeding sprocket l3 and shutter 25, the shutter may readily be properly synchronized with the film movement.

I A front view of shutter 25 is shown in Fig. 2. A

Fig. 7 is a diagrammatic view of a modified ap- 'paratus employing fixed mirrors;

explanatory diagram illustrating an embodiment similar to Fig. 1;

Fig. 15 is a diagrammatic view of an embodiment including the plurality of projection lenses of Fig. 1, the auxiliary deflecting means of Fig. 4, and the additional projection means of Fig. 12.

Referring now to Fig. l, film ll isfed with continuous uniform motion by a film-feeding mechanism including sprockets l2, l3 driven by motor i4. Additional mechanism may be employed, if desired, to insure absolute uniformity of motion. The film is illuminated by a suitable projection lamp l5 and condenser lens IS. The

projection lamp may be a multiple coil tungsten projection lamp, such as illustrated, or other suitable projection source, such as an arc lamp. A front view of the lamp is shown in Fig. 1a. A plurality of fixed projection lenses, generally designated as ii, are interposed between the film II and a suitable television scanning device l8, here shown as a tube of the so-called imagedissector type. The image-dissector tube is provided with suitable longitudinal and transverse deflecting coils l9 and 21, respectively.

Projection lenses 11, here shown as five in number, designated a, b, c, d and e, respectively, are spaced apart longitudinally of the path in which film l I is moved. Light rays 22 are drawn from the film through respective projection lenses to the same point 23 of cathode 24 of the image-dissector tube. From these rays it will be plurality of arcuate slots a", b", c", d" and e" are cut in an opaque disk 25 of suitable material. The arcuate slots are so spaced from the axis 26 of the disk as to uncover the respective lenses (1, b, c, d and e. Th order in which the slots are arranged around the disk, and hence the order in which the respective lenses are uncovered, is determined by the order in which it is successive scansion periods.

If desired, the shutter may be rotated intermittently, instead of continuously, to expose the lenses inproper sequence, thereby permitting the use of a smaller disc with shorter slots. Or, other suitable means, such as light valves, may be employed.

Each projection lens Ila e projects an area lying in the path of travel of the film to a corresponding conju'gate'area of the cathode 24 of the image-'dissector tube, rather than merely a point. Thus, if arrow 2] be considered to be an image recorded on film II, a corresponding image 21' will be formed on the cathode 24 by projection lens I). 'The image-dissector tube may be skewed just enough so that all rays from the I lenses pass by the scanning finger 28, thereby 65 avoiding producing a shadow of, the finger on the cathode. Of course, if the finger is placed at the' In general, the image projected onto cathode 24 by a single lens will correspond to a film- .frame of film II, but since in Fig. 1 the film is continuously moving during scanning, the height of the projected area may be less than the height of a film-frame if the direction of the longitudinal scanningin the image-dissector tube is against the motion of the projected image. This will be more fully described hereinafter. The ratio of the distance from film to projection lens, and the. distance from projection lens to cathode, may advantageously be chosen so as to produce an image on the cathode which is enlarged several times.

seen that light from the fixed longitudinally electrons from cathode 24 which are focused by focusing coil 29 and form an electron image in the plane of the scanning finger 28. This electron image is deflected past the scanning finger by means of coils I9 and 2|, and respective ascomplete a scanning traversal of the moving image 21' on the cathode during the proper interval.

The specific apparatus shown in Fig. 1 is particularly designed for scanning a film moving at the rate of 24 frames per second by the interlaced method with component scansions occurring at the rate of 60 scansions per second. For a more complete understanding of the operation of the apparatus reference may be had to Fig. 3.

In Fig. 3 a fragment of film l I is illustrated in the positions which it occupies at the beginning of successive scansion periods. With a film movement of 24 irames per second and a scansion rate of 60 scansions per second, it Will be understood that two film-frames 'move past a given point in the path of travel of the film in the length of time it takes for five scansions. Therefore, the film moves a distance corresponding to /5H, where H is the distance between success film-frames, during a single scansion period. For this reason the film-frames 33 .and 34 are shown successively displaced a distance of /5H, at the beginning of corresponding scansion periods I, II, III, IV and V, respectively. The scansion periods are /60 second in length, not taking into account the fact that the film-frames may not be quite contiguous to each other.

During scansion period I, the lower film-frame 33 is projected through projection lens a (Fig. 1) and scanned, the scansion beginning at the lower edge of thefilm-frame at point 35 and progressing upwards until it reaches point 36 at the end of the scansion period. Since the filmframe moves downward a distance of H during the scansion pediod, the scansion area need be only H in height in order to completely traverse the film-frame. It will :be understood that although the scanning pattern is actually produced in the scanning tube, in Fig. 3 the dotted scanning pattern is represented as being at the plane of the film. Each scanning area at the film is fiired in space and the-several scanning lens b operative during the second scansion period. The scansion begins again at the lower edge of the film-frame at point 31 and progresses upwards until it reaches point 38 at the end of the scansion period. This is the same as in the first scansion period. For the selected film speed and scanning periods, shutter 25 will rotate at 720 R. P. M.

It is contemplated, at the present time, that the scansions of lower film-frame '33 performed in scansion periods I and II will be interlaced scansions, each scansion producing approximately half the number of lines desired in the complete image. The interlacing may be accomplished in known manner by appropriate control of the saw-tooth oscillators. Or, the position of the lenses may be slightly altered to produce the desired interlacing. For example, lens I; may be spaced from lens a so that the projected images of film-frame 33 occupy not quite the same area of cathode .24 at corresponding instants of scansion periods I and II, but are rela tively displaced just enough to produce the desired interlacing. These different methods of interlacing may also be employed in the embodiments hereinafter described.

If desired, each scansion may be performed so as to produce the full number of lines desired in the final image.

During scansion period III the lower filmframe 33 is again rescanned, lens 0 being operative during this period. With interlaced scansion, the component scansion produced during period III may be a duplicate of the scansion produced in either of the preceding scansion periods.

During scansion periods IV and V, the upper 7' film-frame 34 is scanned in' the same manner as previously described for film-frame 33, lenses d and e being successively operative during these periods. The scansion begins at the lower edge of the film-frame during each scansion period, and progresses upward until it reaches the upper edge of the film-frame, the two scansions being interlaced if desired. The lower film-frame is scanned three times, whereas the upper filmframe is scanned only twice. Therefore, since a scansion period lasts Vco second, two film frames are scanned in of a second, thereby scanning the film-frames at the average rate of 24 per second.

After the completion of the cycle of scansions shown in periods I V, the cycle is repeated to scan the two film-frames next above 33 and 34, and the repetition continues until the desired length of film is transmitted.

From the positions of the film-frames and corresponding scanning areas shown in Fig. 3,

it will be seen that the scanning area at the film is successively displaced longitudinally of the film for successive scansion periods. The longitudinal length of the scanning areas and the relative displacement thereof are shown at a"', b"', c', d and e. Each area is H in length, and areas a', b' and c' are successively displaced by H. This corresponds to the displacement of the film at the beginning of the successive scanning periods. Scanning area 41" is displaced downwards from a' by A, H, since this is the position of the upper film-frame 34 at the beginning of scansion period IV. Scanning area e' is displaced downward from d' by H, to allow for the film movement. It

\ will be understood that the scanning areas a"". e' are all in the plane of the film H and are here shown as spaced apart from left to right for clearness only. The scanning areas are spaced apart longitudinally of the film movement, it beging understood that the spaced areas overlap for the scanning procedure illustrated, and are not completely exclusive.

As previously stated, in order that the position of the scanning pattern produced by the image-dissector tube may remain unchanged for successive scansion periods, despite the change in position of the scanning area at the film, the projection lenses a, b, c, d and e are so positioned with respect to the film that scanning areas a' e' will be conjugate to the same area 39 of the cathode 24 of the image-dissector tube. The correct positioning is shown in Fig. 3 by drawing lines from the extremes of each scanning area a' e' to the corresponding extremes of area 39. The projection lens corresponding to a given scanning area will be placed at the intersectionof the lines drawn from that scanning area.

From geometrical considerations it will be seen that if the distance from the film II to the projection lenses is :r, and the distance-from the projection lenses to the cathode 24 is y, and it is desired to superpose on cathode 24 area which are spaced from each other by a distance H in the plane of film II, as is the case here, successive lenses should be spaced longitudinally from each other by a distance L whose length is determined by the following equation:

Thus, the lenses are slightly closer together than the corresponding areas in the path of travel of film II which it is desired to super-\ finger 28 in the case of an image-dissector tube,

will be determined on the basis of an image of height H, rather than H, in order that the entire area of the film-frame may be covered either by a single non-interlaced scansion, or by two interlaced scansions as is described herein.

From Fig. 3, as Well as from will be seen that the projection lenses I! are quite small. In the illustrated embodiment, using standard motion picture film, they would be of the order of a few millimeters in width. To increase their light gathering power they may be made rather long, as shown in Fig. lb. The lenses could conveniently be obtained by cutting central vertical slices from a corresponding number of standard lenses.

At the point where the-operation is being transferred from one lens to another, the first lens willbe gradually closed ofi and the second lens gradually opened by the respective slots of shutter 25. Therefore during this period the projected images will not have their full lumi- Equaticn 1, it

nosity. This period may advantageously be used for blanking,'so as to permit the electron beam in the scanning tube to retrace its path .to the starting position, and to permit the transmission of frame-synchronizing signals. In practice, film-frames are oftennot quite contiguous to each other, and since this period comes between scansions of the same and successive filmframes, the complete, or very nearly the complete, height of the film-frames may be transmitted.

For simplicity, the space between film-frames has been usually disregarded in the explanations given herein, since such details will be understood by those skilled in the art. The specific embodiment shown in Fig. l employs five projection lenses for the scanning of motion picture film at the rate of 24 frames per second with scansion periods recurring at the rate of 60 scansions per second. so as to coordinate present motion. picture and television standards. The spacing of the lenses and sequence of operation illustrated in Fig. 3 is thought desirable since it permits equal spacing of the lenses and the repeated scansions of a single film-frame are completed before the scansions of the next film-frame are begun. However, other spacings of the lenses and sequences of operation may be employed if desired.

Although the invention is especially concerned with coordinating existing motion picture and television standards, if it is desired to move the film at a rate other than the above, or to employ scansion periods other than the above, the apparatus can be modified accordingly. For example, the apparatus can be modified to transmit film-frames at the rate of 25 pictures per second, interlaced, as is customary in England, in which case only two lenses needbe employed since each film-frame is scanned twice and the individual scansions recur at the rate of 50 scansion per second. In such case the film would move H during a scansion period, so that a s ngle scanning area at the film need be only H in height.

Another example which might be mentioned is that of scanning film at the rate of 20 pictures per second with scansion periods of of a secand. For this case 3 projection lenses would sufiice, the film would move H in a scansion period, and a single scanning area at the film would be H in height. Each film frame would be scanned 3times either by double interlacing with duplication of one scansion, or by triple interlacing.

With different film and scansion rates, including those just mentioned, the spacing of the lenses will be selected accordingly. When the successive scansion periods are equal and alike, the spacing of the lenses and the sequence of their use will in general be such that corresponding parts of the same and successive projected film-frames will coincide at the plane of the cathode of the image-dissector at corresponding instants in the respective scansion periods. Thus, at the beginning of any scansion period, the image of the film-frame being projected in that period should occupy the same area as that occupied by previous film-frame images at the beginning of their respective scansion periods. Stated somewhat differently, the spacing and sequence of use of the lenses should be selected so that corresponding elemental areas of the same and successive film-frames occupy- 60 scansions per second, a spacing of the areas at the film of H may be employed.

It is believed that the above discussion of several scanning procedures and rates will sufiice to indicate how the apparatus can be designed for any particular set of conditions.

As previously stated, the projection lenses ll of Fig. 1 are quite small. Various optical expedientsmay be employed in order to increase the spacing between the lenses, and hence permit the use of larger lenses. Also, a single auxiliary lens could be used for correction, if desired. However, it isadvantageous to be able to use only a single projection lens, whose size can be increased as desired to collect a suit!- clently large cone of light. Fig. 4 shows such a system. The system can be so designed that a standard highly corrected projection lens can be employed.

Referring now to Fig. 4, an embodiment of the invention is illustrated employing a single projection lens and an intermittently moving mirror, instead of the five projection lenses shown in Fig. 1. Film H is moved with continuous uniform motion by sprockets l2, l3 and motor l4, as in Figjl. Projection lamp l5 and lenses 4i and 42 illuminate the desired film area. Projection lens 43, oscillating mirror 44 and the stationary mirror 45 project an image of film II to the cathode 24 of the image-dissector tube It, the intermittently moving and stationary mirrors being between the projection lens and the image-dissector tube, in an optical sense. The image-dissector tube is provided with focusing coil 29, deflecting coils l9 and 2|, and associated saw-tooth oscillators 3| and 32, as in Fig. 1. The tube is also provided with auxiliary coils and associated mechanism, described hereinafter. The dissector tube is skewed with respect to the beam of light coming from mirror 45, so that the beam is not intercepted by the finger 28 of the tube.

Mirror 44 is preferably plane-faced, although it could be provided with a small curavture, if desired, and is successively oriented in a plurality of different angular positions so as to cause different areas in the path of travel of film II to be successively projected onto the same area of the cathode 24. To accomplish this, the mir ror 44 is mounted on lever arm 45 which is pivoted at the mirror by pin 50. The angular position of mirror 44 is determined by cam 46, driven by motor I4. Cam 46 is provided with cam surfaces j, g, h, i and 9', upon which pin 47, mounted on lever arm 45, rides. Each cam surfaceis an arc of a circle, the radii of the circles being selected in accordance with the desired scanning scheme. I

If the scanning scheme is to be the same as that shown in Fig. 3, the radii would be selected so that mirror 44 successively assumes orientations such that rays from points I, g, 711,2" and 7" (corresponding to points a e in Fig. 1) are caused to impinge successively on the same point 23 of the cathode of the image-dissector tube. Of, course, for each position of mirror 44, an area of the film ll, rather than a mere point thereof, will be projected onto the cathode of the image-dissector tube. For this scanning scheme the motor it will cause the cam to make one revolution during the interval in which two film-frames move past a given point in the filmfeeding mechanism. For a film speed of 24 frames per second, the cam will rotate 12 revolutions per second.

Cam 46 rotates counterclockwise, as indicated. Thus pin 41 must be pushed outwards in passing from cam surface 7', to surface f, and also when passing from cam surface It to 1'. Projecting arms 48 and 49, mounted on the same shaft as the cam 46, but axially displaced therefrom,

are provided for this purpose. These arms engage the pin 5|, which is affixed to the lever arm 45, and push the lever arm outwards at "the proper times. Thus arm '48 engages pin 5| just before pin 41 reaches the junction-point between cam surfaces 1 and I. The length of pin 5|, its distance from the pivot point of lever 45, and the length of arm 44 should be so proportioned as to push the lever arm 45 outwards in a comparatively short period of time. For example, a length time corresponding to about 5- of a scanning od or less, is suitable, since this interval is commonly used purposes between scansions anyway. Arm 49 engages pin 5| in a similar manner in order to move pin 41 outwards in passing from cam surface h to i.

The dimensions of the cam and the lever arm 45 have been'greatly exaggerated in order to illustrate clearly the principles involved. It will be understood that the angles through which the mirror 44 is turned will ordinarily be quite small, of the order of one or two degrees. The

exact angles to which the mirror must be turned will be determined by the dimensions of the apparatus and the spacing of the points ,1" h

which it is desired to superpose at the imageof two or three different orientations of mirror.

44, instead ofthe five shown, would correspond to the use of two or three projection lenses in Fig. 1.

The purpose and operation of the auxiliary deflecting coils 52, 53, and their associated mechanism will now be described. It will be appreciated that the orientation of mirror 44 in each of its several positions must be quite precise in order to secure proper scanning of the film. This necessitates accurately designed and constructed cams and cam followers to produce the required motion. If other means for changing the orientation of the mirror are employed, they also must be quite precise. In practice, due to the difiiculty or expense involved in making a very accurate cam, or due to wearing of the surfaces during use, the orientation of mirror 44 in each of its positions may not be precisely correct.

By slightly altering the position of the electron image with respect to the finger 28, in the imagedissector tube, any inaccuracies in the orientation of mirror 44 may be compensated for.

Auxiliary coils 52, 53 permit of a comparatively quick and accurate adjustment of the position of the scanning pattern produced in the imagedissector tube during the scansion periods.

The auxiliary coils are energized with a periodically varying electric wave by means of commutators 54 and. 55, respectively, driven by motor 14. Each commutator has five segments, one for each scansion period. The .segments of commutator 54 are connected to conducting rings 56, 51, 58, 59 and 60, respectively, and each of the conducting rings is adjustably connected to a potentiometer 6| energized by battery 62. For a fuller description of the construction of the for blanking commutator, reference may be had to my prior application Serial No. 115,113,.fi1ed December 10, 1936. p 1

One end of coil 52 is connected to the potentiometer 6i, and the other end is'connected to in the path of the "rays through projection-dens 43 and near the lens, and are spaced apart longibrush'63 which rides on the commutator segmerits. It will thus'be seen that the coil 52 may be successively energized with a succession of constant voltages obtained from the segments of commutator 56, each voltage lasting throughout a scansion period, and thus periodically deflect the scanning beam. The amount of deflection of tudinally with respect to the path of travel of film H. The mirrors could be spaced apart laterally of the film, but this is not preferred for reasons given in connection with Figs. 7-11. Light rays impinging on these mirrors are reflected to the plane mirror 45 and thence to the cathode 24 of the image-'dissector tube Hi. The orientations of mirrors k o are such that corresponding points is, Z, -m', n and o' in the path of travel of film II are caused to impinge on the same point 23 of the cathode of the image-dissector tube. Mirror 45 is advantageously positioned so that the light paths from the film to the image-dissector tube are the same for each mirror. Each mirror It o reflects rays not only from the corresponding point in the path of the film, but rays froma corresponding area in the path of the travel of the film. The shutter 25 is similar to that shown in Fig. 2, and exposes the mirrors 7c o in the proper sed :ence. The shutter is driven by motor M which rect position in a longitudinal direction, this displacement can be corrected by displacing the electron image corresponding to that area the proper amount in the opposite direction by adjusting the corresponding tap on potentiometer 6!. image in a direction at right angles to the film movement may be corrected by adjusting the corresponding tap on potentiometer 64.

Instead of using additional coils for the purpose just described, the several constant'deflecting voltages might be applied to the regular defleeting coils,'although the separate coils shown are preferred in order to prevent the auxiliary currents from affecting the regular deflecting currents. If a scanning tube were used which employed electrostatic deflection, the apparatus -could be appropriately modified. Also, means Similarly, a displacement of a projected other than commutators, might be used to gener- .pne commutator need be employed.

Fig. 5 illustrates scanning apparatus which has been found to give good results. This system is similar to that of Fig. 4 in that only a single projection lens is employed, but differs in that instead of employing an oscillating mirror which is cyclically shifted through a plurality of difierent orientations, a corresponding plurality of fixed mirrors, whose orientations correspond to the several positions of the oscillating mirror, are employed; By this means, difficulties encountered in rapidly yet accurately changing the orientation of a single mirror, particularly inmodem high-definition systems, are avoided. Other advantages, which in part will be obvious and in part will be pointed out hereinafter, are also present- The various parts of the system, with the exception of the fixed mirrors and the shutter, have been described in connection with Fig. 4 and hence the description will not 'be repeated.

also drives the film-feeding mechanism, and hence proper synchronization can be obtained.

The functioning of the apparatus is similar to that of Fig. 1, described more fully in connection with Fig. 3. Since, however, the projection of different spaced areas in the path of travel of the film to thesame area of the image-dissector tube is accomplished by the use of a single projection lens with associated mirrors k to 0, rather than a plurality of individual projection lenses, the positioning of' the mirrors It to o is not as restricted as that of the projection'lenses of Fig. 1. The mirrors may be adjustably mounted so that they can be precisely orientated to give the proper placementof the images in the imagedissector tube.

Usually, the orientation of the fixed mirrors in Fig. 5 willbe such, as in the case of the previously described figures, that at corresponding instants in respective scansion periods the same portion of a given film-frame, or corresponding portions of different film-frames, will be scanned. Ordinarily, when each film-frame is scanned in transverse lines beginning at the bottom of the frame, the selected area of cathode 24 will be rendered successively conjugate to different longitudinally spaced areas whose separation is such that at the beginning of any scansion period the bottom of a frame is in position to be scanned. Ifthe same film-frame is scanned a plurality of times, the separation of the corresponding scanning areas at the film will be the distance the film moves from the beginning of one scansion period to the beginnin of the next. When' two difierent film-frames are scanned, the

' corresponding scanning areas at the film will be separated by the distance between the filmframes as modified by the movement of the'fllm between the corresponding scansion periods. In the embodiments described ,hereinbefore, the order of rescanning the same film-frame and of scanning adjacent film-frames has, been chosen so that the'separations between adjacent scanning areas at the film are all equal. Although this is advantageous, a scanning scheme might be selected in which this is not true, and the apparatus designed accordingly.

The proper orientation is facilitated byplacing in the plane of the film l l a glass plate which has lines of the desired spacing ruled thereon. Plane mirrors, k, 1, m, n and, 0 are positioned 7 Such a glass plate is shown in Fig. 6. The

, proper place on the cathode.

space between lines is H to correspond to the distance between the scanning areas a', d, b', e', c' (in the order given) of Fig. 3. The mirrors can conveniently be adjusted by rotating shutter 25 so that half of minor k and half of mirror I are exposed, and then adjusting one or both mirrors so that the projeced images of the corresponding lines It" and l" of the glass plate are superposed at the cathode 24 of the image-dissector tube, and are located at the Then the shutter is rotated to expose half of mirrors 1 and m, and mirror m adjusted so that the image of its line m" is superposed on that of I". Then mirrors n and are successively adjusted in similar manner.

A front view of mirrors k to 0 is shown in Fig. a. The dimensions of the mirrors may be chosen in accordance with the other elements of the system. Mirrors 3 mm. in width and mm. in height have been found satisfactory. In

order that the projected image formed by each mirror may be of the same illumination, it may be necessary to slightly decrease the effective area of one or more of the mirrors. This may be conveniently done by masking ofi a portion of the lower part of the mirrors, as indicated in the case of mirrors n and o.

In order to secure eflicient and even illumination over the entire area of a single image, itis advantageous to image the projection lamp II at the projection lens 43, or approximately at the plane of the mirrors, or at some plane in between. This maybe accomplished by suitably designing and positioning the lenses ,and 42. The image should of course cover all the mirrors. It is also advantageous to place the axes of the coils of the projection lamp I5 longitudinal with respect to the film l I, so that each of the mirrors k to 0 will receive light from each coil. Furthermore, it is advantageous to orient the mirrors so that the upper mirror corresponds to the lower area at the film, and the lower mirror corresponds to the upper area at the film, as is the case in Fig. 5. v

The image-dissector tube may be skewed as in Fig. 1;to permit the light rays to pass the finger 28. If the finger 28 were behind the cathode, this skewing could be dispensed with, unless it should be desirable in order to equalize the light paths to various parts of the cathode, or for any other reason.

The operation of the apparatus of Fig. 5 will be understood from the description previously given for Figs. 1 to 4. Mirrors k o are .rendered successively operative by shutter 23,

\ proceeds toward the top at a rate which will scan the frame in the required time. Since the film is moving H during the scansion period, the height of the scanning pattern need be only H as magnified. This procedure will be understood by reference to Fig. 3 and the description of that figure.

The system of Fig. 5 can be adapted to scanning schemes other than that illustrated, as discussed in connection with Figs. 1 and 4. The number of mirrors employed, their orientation, and the order in which they are exposed will be selected in accordance with the selected scanning scheme.

The auxiliary deflecting coils B2 and I3 shown in Fig. 4, and their associated commutators, might also be used in the apparatus of Fig. 5, ii desired It will be appreciated that the accurate and precise adjustment or the orientation of the mirrors k to o is a rather delicate operation. Thus, if it should be discovered just prior to the .broadcasting of a program that one or more of ply a more or less permanent correction for inaccuracies in mirror orientation.

Referring now to Fig. 7, apparatus is shown which is especially adapted for the scanning of film at the rate of 30 pictures per second, interlaced, with component scansions occurring at the rate of 60 per second. As in the previously de- 4 scribed embodiments, a film II is fed with-continuous uniform motion by means of sprockets I2, I: and motor I4. In this figure, the projection lamp system comprises a, projection lamp I5, a reflector 65 positioned behind the projection lamp, and a pair of lenses 86, 61. This system is so designed as to uniformly illuminate the desired area of film ll.

In the previous embodiments a scanning tube of the image-dissector type has been illustrated. Fig. 7 illustrates the use of a mechanical scanner comprising a scanning disk H, a lens 12 and a photoelectric cell 13. Images of spaced areas in the path of travel of film II are projected to the same, or substantially the same, area -in the plane of the scanning disk H, by means of the projection lens 43, and the differently oriented mirrors 1), q, and their respectively associated mirrors 68 and 69 positioned between the projection lens and the scanning disc, in an optical sense. This mechanical scanner can be employed in the other embodiments of the application, if desired, or other suitable scanning devices may be employed. However, it is preferred at the present time to employ a scanning tube of the image-dissector type.

,The scanning disk 1| is provided with a suitable spiral of holes to repeatedly scan images projected to the plane of the disk. Light passing through the scanning holes is converged by lens 12 to the photoelectric cell 13, to produce corresponding electric signal waves.

In Fig. 5, the plurality of mirrors k o were spaced apart longitudinally of the film, and rays from each of these mirrors were diverted to the image-dissector tube by means of a single mirror 45. In Fig. 7, the mirrors p and q are separated transversely of the film, and are oriented so that mirror p reflects rays from the projection lens upwards to mirror 68, and the latter reflects the rays to the plane of the scanning disc 1|. Similarly, mirror q reflects rays from the projection .lens downwards to mirror 69, which in turn reposing mirrorsp and q. This shutter may be similar to that shown in Fig. 2, but will be provided with two slots (01', an even number of slots) instead of five.

The operation of the apparatus. of Fig. 7 can be explained by means oi'a diagram such as that of Fig. 3. However, since the apparatus is somewhat simpler than that shown in the previous figures, it is feasible to illustrate the operation as shown in Fig. 8. Referring to Fig. 8, a single film-frame 16 is shown in the positions which it occupies at the beginning oitwo successive scansion periods. Since the film moves a half frame during a scanslon period, the two positions are separated by V, H. The scansion begins at the bottom or the frame and progresses upwards.

Due to the film motion, the scanning area at the film need be only V2 H' in heighth, as shown by the shaded area of the film-frame. At the beginprogresses downwards.

At the beginning of the second scansion period the film-frame 16 is at position B and is projected by means of mirrors 2), and 68 to the area in the plane of the scanning disc shown at B. During this scansion period the shaded area is again scanned by the scanning disc, the scansion beginning at the topof the shaded area and progressing downwards.

It will be clearly seen from the diagram that although the shaded areas at A and B, representing the areas in the path of travel of the film which are actually scanned, are longitudinally displaced, the shaded areas at A and B.

representing the areas in the plane of the scanning disc scanned during the respective soansion periods -coincide at the scanning disc. Thus, the recurrent scanning pattern of the scanning disc is stationary. Successive film-frames are scanned in the same manner as film-frame l6.

Figs. 9 to 11 illustrate a further embodiment of the invention especially adapted, like that of Fig. 7, for the 'scansion of film for moving at the rate of 30 frames per second with component scansions recurrent at the rate of 60 per second. The apparatus of Figs. 9 to 11, however, possesses certain advantages over that of 'Fig. 7. In Fig. 7 it is found that the projected images are rather unevenly illuminated from left to right of the images, and that the relatively bright portions of the images formed by mirrors p and q are on opposite sides of the respective'images. This gives rise-to a rather objectionable fiicker from left-to right of the images, unless aditional means are employed for eliminating the flicker. The unevenness of illumination over the area of a single image is probably due to the fact that the mirversely of the fihn, and are separated longitudinally thereof. Thus the centers of the utilized areas of the mirrors are separated in the direction of motion at the mirrors of the rays forming the film images, but are not substantially separated in the direction transverse thereof. Of J course, no images of the film are formed at the more, due to the fact that the height of the scanning area at the cathode is only a fraction of theheighth of the projected film-frame, the scanning area at the cathode 24 may be illuminated more evenly. For this reason, an objectionable flicker is not produced;

As shown in Fig. 10, mirrors p and q are oriented so that the rays from the projection lens 43 are deflected transversely to a single mirror TI, and mirror 11 in turn reflects the rays to the. plane of the cathode 24 of the image-dissector tube. As seen from the 'end view .of the mirrors (Fig. 11), mirror 12 is tilted so as to slightly defiect the rays from the lens downward, and mirror q is oriented so as to slightly deflect the rays upward. This causes two separated areas in the path of film ll to coincide at the plane of the cathode 24. i

Due to the fact that mirrors p and q are side by side in approximately a plane, and both reflect to the same mirror I1, the light paths from the film to the plane of cathode 24 may readily be made equal for the two mirrors. Also, considerably more latitude in the axial positioning of the scanning device is allowed since the beams from the two mirrors come to the scanning device from very nearly the same direction, rather than intersecting at a considerable angle as in Fig. 7. These are further advantages of this embodiment over that of Fig- '7.

The operation of the apparatus of Figs. 9 to 11 is the same as that of Fig. 7 and hence will not be described again. It will be understood that suitable deflecting coils and circuits are provided for tube i8, as in previous figures, these being omitted here for simplicity.

the plane 88, is illustrated by light rays 19. As

shown, the light rays 19 are converged by projection lens is, and the converging rays are refiected by mirror I" to 23', at which point the rays meet and form the image. Each of the other mirrors k, m, n and 0 form images of points k,

m, n and 0', respectively, at points 23' in plane 18. Thus, the images formed in plane 18 correspond to those formed on the cathode 24 of the image-dissector tube in Fig. 5.

The images in plane 18 are projected by means of projection lens onto the cathode 24 of the image-dlssector tube I8, an image of point 23' being formed at point 23 on the cathode. The image-dissector tube may be skewed so that all rays from lens 80 pass the scanning finger 28.

The mirrors k to o are rendered successively operative in proper sequence by shutter 25, as in Fig. 5, and the corresponding moving images of the film ll formed on cathode of the image-disin a plane, such as plane 18, and then projected by the additional lens to the scanning device.

Referring nowto Figs. 13 and 14, apparatus is shown similar to that of Fig. 1 in employing a plurality of small lenses 1', s, t, u, 12, but also employing an additional positive lens 82 which acts in conjunction with each of the small lenses to form images of corresponding spaced fixed areas in path of travel of film II at the same area of the scanning device, here shown as a tube l8 of the image-dissector type. The advantages of using this type of optical system in film-scanning apparatus of the kind herein disclosed are that the system can be designed so that the separation between adjacent lenses 1- v is greater than that of Fig. 1, and indeed, greater than the separation between successive areas at the film which are to coincide at the image plane of the scanning device, and also that the adjustments necessary to focus the film images sharply at the scanning device and to make the images corresponding to the several small lenses of precisely the same size are to a large extent separated.

The great separation is desirable in order to avoid the necessity for using very small lenses,

or lens segments, which may be diificult to construct with suitable correction and which of course restrict the amount of illumination which can be utilized from a given source. The separate adjustability of focus and relative image size is also advantageous. In Fig. 1, any change in the positioning of one of the lenses to secure good focus at the same time changes the size of the image. Unless the lenses are precisely of the same focal length this ma be serious, and in practice it is difficult and expensive to obtain corrected lenses of precisely the same focal length.

In Fig, 13, a mirror 65' is employed to collect light from the projection source, here shown as a filament projection lamp l5, from as large a solid angle as practicable. Lenses 83 are designed to collect light from the projection source and form an image of the source between lenses 83 and the field lens 84. Although any other suitable projection light system may be employed, if desired, this type is advantageous since the source l5 itself is removed from the vicinity of the film, thereby avoiding undue heating of the film, but the image of the source is close to the film, thereby securing eflicient illumination. This image may in turn be focused at a suitable plane in the system, it being found advantageous to focus it betweenlens 82 and the small lenses, at a short distance from the latter.

Broadly stated, the projection system of Fig.

13 has means for forming an enlargedimage of the film, and means for successively projecting images lying at spaced areas of the plane of the enlarged image to substantially the same area of a selected image plane at which the projected images'are scanned. Although different optical designs may be employed for forming the enlarged image, and for projecting different spaced areas thereof to the scanning device, the system shown is at the same time relatively simple, efficient and compact.

Calculations indicate that so longas the image which is utilized as an object by the lens segments is an enlarged image the separation of the lens segments for a given over-all magnification of the film images will be greater than in the case of Fig. 1. In general, the greater the enlargement of the image used as object by the lens segments, the greater will be the separation.

Projection lens 82 is of such focal length and so positioned from film II that the film is inside the principal focus of the lens, so that an enlarged virtual image of the film is formed behind the film, for exampleat plane 85 of Fig. 14. Thus areas a', d, b, e, c' (Fig. 3) which are spaced apart, in the order given, a distance of H at the film, are spaced apart at the image plane 85 (Fig, 14) by a distance A; M X .Mag., whereMag. is the magnification between the film and the plane of the virtual im age. The corresponding areas in Fig. 14 are in-.

dicated as r, 11., s, v, t, respectively.

The virtual images of the portions of the film at r v serve. as objects for the respective lenses 1' v. The latter lenses have such focal length and are so spaced longitudinally of the filrn movement that the images at the respec- ,tive areas of plane 85 are projected to substantially the same area' 3.9 of the cathode 24 of the tube 3. If another type of scanning device is employed, it will be so positioned as to scan the images projected to area 39 of image plane 24.

By suitabl selecting the focal length and position of lens 82, the separation of the areas 1" made large enough so that with suitably selected .focal lengths and axial positions of lenses 1' v, the separation of the latter lenses longitudinally of the film movement may be greater than those in Fig. 1. Also, with suitable design it is found that the focusing of the film images at plane 24 may be primarily adjusted by moving lens 82 alone in the-axial direction, while movement of lenses r. v in the axial direction changes the focusing of the images to a much smaller extent than an equal movement of lens 82. However, movement of lenses 1' v in the axial direction will permit adjusting the relative sizes of their respective images. Thus the several pro jected images may be readily made of equal size,

all in goodfocus. of course be simultaneously adjusted by moving lens 82, with appropriate change in the position of the scanning device if necessary.

going description are given, it being understood that'the specific details are given by way} of ex-,

' ample only, and that the invention is in no way limited thereto, since some or all of the details.

of the design may be changed by those-skilled in v at the virtual image plane may be The size of the images. can I the art to meet the requirements of a particular situation, or as they deem advisable.

wide and 1 /2 in. long in order to gather a comparatively large amount of light. achromatic doublets may m used for these lenses, if desired. Lens 82 is preferably a rather highly corrected lens.

Ihe embodiment of Fig. 13 has been found to have considerable advantages over that of Fig. in ease and precision of adjustment, and also in ease of maintenance. Furthermore, the congruency of the several images at plane 24 is found to be more exact with the apparatus of Fig. 13, and loss of light is considerably reduced.

Fig. is an embodiment of the invention including the projection lenses of Fig. l, the auxiliary deflecting coils and commutators shown in Fig. 4, and the additional projection lenses til of Fig. 12. The operation of the apparatus will be clear from, the discussion given hereinbefore, and therefore need not be described in detail here. 'The projection lenses iii operate in the manner described in connection with Fig. 1 except that the successively superimposed images formed by lenses iii are formed at plane it, rather than at the cathode 2 3 of the scanning tube is. The images at plane it are then projected to the cathode 26 by the additional projection lens at, as described in connection with Fig. 12. The auxiliary deflecting coils 52 and 53, and their associated commutators 54 and 55 driven by the same motor N which drives the shutter and the film moving mechanism I3, operate in the manner describedin connection with Fig. 4. By the use ofthe auxiliary coils and oommutators slight changes in the position of the scanning pattern during different scansion periods may be quickly and accurately made so as to compensate for slight inaccuracies in the positions of lenses l1.

It will now be apparent that this invention provides a method of scanning film which is particularly valuable in the scanning of a continuously moving film, and especially adapted for coordinating present day sound-motion-picture and television standards, and several forms of apparatus whereby this method can be carried out. In general it might be said that the several embodiments of the invention described herein each possess certain advantages over the others. depend somewhat upon the conditions under which the apparatus is to be used, and also upon individual judgment.

It will be apparent that many changes may be made in the details of the embodiments described herein without departing from the spirit The particular embodiment selected will and scope of the invention. Also, features of several embodiments may be combined, it desired.

I claim:

1. Television film-scanning apparatus which comprises a film-feeding mechanism, a source of projection light positioned to illuminate a film in said film-feeding mechanism, a projection system comprising a plurality of fixed projection lenses spaced apart in the direction in which said film is moved, said projection system being positioned and adapted to project film images lying in a. plurality of areas separated in the direction in which the film is moved to substantially the same area of a selected image surface, the spacing of said lenses being selected so that said plurality of areas are separated by distances substantially different from the separation of film-frame areas of the film, a scanning device positioned and adapted to scan a projected image lying in said area of the selected image suriace, and means for rendering said projection lenses operative successively one at a time.

2. In television transmission systems, apparatus for scanning a continuously moving-film bearing motion picture film-frame images which comprises a film-feeding mechanism constructed and adapted to feed a film longitudinally with continuous motion, a source of projection light positioned to illuminate a film in said film-feeding mechanism, a plurality of fixed projection lenses spaced apart in the direction in which said film is moved, said lenses being positioned and adapted to project film images lying in a corresponding plurality of longitudinally separated areas in the path of travel of said film to substantially the same area of a selected image plane, means for rendering said projection lenses operative successively one at a time, and a scanning device positioned and adapted to scan moving images of said film lying in said selected image plane; the rate of feeding the film, the spacing of said lenses, the means for rendering said lenses operative, and the period of the scanning device being correlated so that corresponding parts of the projected film-frame images are scanned at substantially the same part of the said selected image plane. I

3. In television transmission systems, apparatus for scanning a continuously moving film bearing motion picture film-frame images, in which afilm-frame. is scanned a plurality of times, which comprises a film-feeding mechanism constructed and adapted to feed a film 1on- 'gitudinally with continuous uniform motion, a

source of projection light positioned to illuminate a film in'said film-feeding mechanism, a plurality of fixed projection lenses spaced apart in the direction in which said film is moved, said lenses being positioned and adapted to project film images lying in a corresponding plurality of longitudinally separated areas in the path of travel or .said. film to substantially the same area of a selected imageplane, the spacing of said lenses being selected so that said plurality of areas are separated by distances substantially different. from the separation of filmframe areas of the film, means for rendering said projection lenses operative successively one at a time in a selected sequence, and a scanning device positioned and adapted to periodicallyscan moving images of said film lying in said areaof the selected image plane and develop signals therefrom, the scanning of said area by said scanning device extending both longitudinally and transversely of the projected images,'the

spacing of the lenses being correlated with the film speed and the longitudinal scanning period parts of the same and successive projected filmframe images substantially coincide at the said selected image plane when said parts are scanned in their respective scansion periods.

4. In television transmission systems, apparatus for scanning a continuously moving film bearing motion picture film-frame images, in which a film-frame is scanned a plurality of times, which comprises a film-feeding mechanism constructed and adapted to feed a fllm longitudinally with continuous uniform motion, a source of projection light positioned to illuminate a film in said film-feeding mechanism, a plurality of fixed projection lenses spaced apart in the direction in which said film is moved, said lenses being positioned and adapted to project film images lying in a corresponding plurality of longitudinally separated areas in the path of travel of said film to substantially the same area of a selected image plane, a shutter positioned and adapted to render said projection lenses operative successively one at a time in a selected sequence, and a scanning device of the imagedissector type positioned and adaptedto periodically scan moving images of said film projected to said area of the selected image plane and develop signals therefrom, said scanning device being provided with deflecting means for scanning said area both longitudinally and transversely of the projected images in lines extending transversely thereof, the shutter and the.

longitudinal scanning period being correlated so that the lenses are successively operative-during respective successive longitudinal scanning periods, and the spacing of the lenses being correlated with the rate of film feed and the longitudinal scanning period so that, when said lenses operate in said selected sequence, longitudinally corresponding parts of the same and successive projected film-frame images substantially coincide at the said selected image plane at corresponding instants in their respective longitudinal scanning periods.

5. Television film-scanning apparatus for scanning a uniformly moving film having filmframes recorded thereon, in which the periodicity of scanning said film-frames is not an integral multiple of the rate of movement in frames per second, which comprises a-film-feeding mechanism constructed and adapted to feed a film longitudinally with continuous uniform motion at a selected number of frames per second, a projection light source positioned to illuminate a fihn in said film-feeding mechanism, a plurality of fixed projection lenses spaced apart dinal scanning being not an integral multiple of said selected number of frames per second, and means for rendering said projection lenses operative successively one at a time in a selected sequence, said means and the longitudinalscanning period being correlated so that the lenses are successively operative during respective successive longitudinal scanning periods, and the comprises a film-feeding mechanism, a projection system optically arranged and adapted to render a plurality of relatively separated selected areas in the path of travel of a film in .said film-feeding mechanism successively conjugate to substantially the same area of a selected surface, an electronic scanning device provided with means for deflecting an electron beam v in said device to develop a scanning pattern,

at least one of said areas rendered conjugate to,

said selected plane, the magnitudes of said plurality of deflections being adapted to compensate for lack of coincidence at said selected plane of the selected areas successively rendered conin the direction in which said film is moved, said lenses being positioned and adapted to project film images lying in a corresponding plurality of longitudinally separated fixed areas in the path of travel of said film to substantially the same area of a selected image plane, the spacing of said lenses being selected so that said plurality of areas are separated by distances substantially different from the separation of film-frame areas of the film, a scanning device positioned and adapted to periodically scan moving images of said film projected to said area of the selected image plane'both longitudinally and transversely of the projected images in lines extending transversely thereof, the periodicity of the longitujugate thereto.

'7. Television film-scanning apparatus which comprises a film-feeding mechanism constructed and adapted to feed a'film longitudinally with continuous motion, a projection system including optical means successively operative to render a plurality of relatively separated selected areas in the path of travel of a film in said filmfeeding mechanism successively conjugate to substantially the same area of a selected plane, an electronic scanning device positioned with respect to said selected plane so as to scan the portions ,of the film lying at the said selected areas in the path of travel of the film when those areas are rendered conjugate to the said area ofthe selected plane, said electronic scanning device being provided with means for deflecting I an electron beam therein to develop. a recurring scanning pattern to repeatedly scan said area of the selected plane, and means correlated with the successive operation of said optical means for periodically deflecting said electron beam through a plurality of deflections each of which is substantially constant throughout the scansion of at least one of said areas rendered conjugate to said selected plane, the magnitude of said plurality of deflections being adapted to compensate for lack of coincidence at said selected plane of the selected areas successively rendered conjugate thereto.

8. Television filmscanning apparatus for scanning film-frame areas of a film which comprises a film-feeding mechanism constructed and adapted to feed a film longitudinally with 

